paragraph about redux

Rewritten-docs.md

@@ -3111,11 +3111,22 @@ The only part of the state which is persisted is the token of the logged in user
 is kept in cookies and in the local storage. Keeping the token in the cookies is necessary
 for server-side rendering.
 
-#### Redux Middleware
+#### Redux
+
+The in-memory state is handled by the *redux* library. This library is storngly insipred
+by the [Flux](https://facebook.github.io/flux/) architecture but it has some specifics.
+The whole state is in a single serializable tree structure called the *store*. This store
+can be modified only by dispatching *actions* which are Plain Old JavaScript Oblects (POJO)
+which are processed by *reducers*. A reducer is a pure function which takes the state
+object and the action object and it creates a new state. This process is very easy to
+reason about and is also very easy to test using unit tests. Please read the
+[redux documentation](http://redux.js.org/) for detailed information about the library.
+
+##### Redux Middleware
 
 @todo
 
-#### Accessing The Store Using Selectors
+##### Accessing The Store Using Selectors
 
 @todo